1. Field of the Invention
This invention relates to an acoustic control system for an electronic musical instrument, for controlling acoustic characteristics of the electronic musical instrument having a musical instrument body and a speaker removable from the musical instrument body.
2. Description of the Prior Art
In general, a conventional electronic musical instrument (e.g. an electronic piano) has a musical instrument body (piano body) and a stand integrally formed with the musical instrument body. As for speakers of an electronic piano constructed as above, there are two types of arrangement thereof, i.e. one in which speakers are mounted in a piano body alone and the other in which different types of speakers for different frequency ranges are mounted in a piano body and a stand, respectively. In the latter type, the speaker system as a whole is acoustically designed such that optimal acoustic characteristics can be obtained assuming that the both types of speakers are used simultaneously. Recently, another electronic piano of a portable type has been proposed which is comprised of a piano body compact in size with integrated speakers and a stand removable from the piano body. This portable electronic piano is advantageous in that the piano body is portable without necessitating much space, and further, since the piano body has the integrated speakers, it is possible to play anywhere with the piano body alone.
However, in the above conventional portable electronic piano, the piano body has a casing with a limited internal space, and hence it is impossible to increase either the diameter of each speaker or the number of the speakers. Therefore, sound from the electronic piano is rather powerless particularly in the low-frequency range, which makes it difficult to obtain excellent acoustic characteristics. A possible solution to this problem, for instance, is to employ the speaker system used in the above-described electronic piano of the latter of the stand-integrated types and arrange a speaker for the low-frequency range in the removable stand for increased output of low-frequency components. In this case, however, the speaker system including the two types of speakers is acoustically designed such that optimal acoustic characteristics can be obtained by the system as a whole. Therefore, when the piano body alone is carried somewhere and played, low-frequency components which should be output from the speaker in the stand are lost, and only mid-frequency and high-frequency components are output from the speakers in the piano body, so that the acoustic balance is lost, which makes it impossible to obtain excellent acoustic characteristics.